Target classifications

Based on the data collected for each target, the KMC has constructed a high level classification scheme, termed the Target Development Level (TDL). TDL characterizes the degree to which they are studied or not studied, as evidenced by publications, tool compounds and other features. The TDL scheme serves as the primary grouping of targets, clearly delineating those targets that are unstudied (labeled Tdark) from those that have more information about them (labeled Tclin, if associated with approved drugs with known mechanism of action (10), Tchem, if associated with small molecule activities in ChEMBL or Tbio if not associated with small molecule or drug activities but have a GO MF or BP leaf term annotated or else have a confirmed OMIM phenotype). DrugCentral (11) aggregates target-disease information, drug target bioactivity data, which are used to categorize Tclin and Tchem, and feeds into TCRD. See http://juniper.health.unm.edu/tcrd/ for a more in depth description of the TDL classification scheme. Along with the TDL scheme, we have employed DTO to support a formal classification and annotation of the IDG protein families, building on top of prior classification schemes for kinases (13), GPCRs (12–14), ion channels (15) and nuclear receptors (13). Though the DTO, being an ontology, allows for sophisticated inferencing and hypothesis generation, Pharos currently employs the DTO primarily as a simple classification scheme to complement the TDL categories.